From the Guidelines
For fungal keratitis, antifungal medications are the preferred treatment over antimicrobials (antibiotics) due to their effectiveness in targeting fungal cell structures. The treatment of fungal keratitis typically involves the use of topical antifungal agents, such as natamycin 5% for filamentous fungi or amphotericin B 0.15-0.3% for yeast infections, applied hourly for the first 48 hours, then every 2 hours for 4-7 days, followed by gradual tapering based on clinical response 1. Oral antifungals like voriconazole (200mg twice daily) or itraconazole may be added for deep infections, as suggested by the guidelines for the treatment of Aspergillus infections 1.
Key Considerations
- Antimicrobials like antibiotics (e.g., moxifloxacin, ciprofloxacin) are ineffective against fungi because fungi have different cell structures than bacteria, with ergosterol-containing cell membranes and chitin-based cell walls that antibiotics cannot target.
- Antifungals work by disrupting fungal cell membranes or inhibiting essential fungal processes.
- Treatment should continue until complete resolution, typically 4-8 weeks, and may require corneal debridement to remove necrotic tissue and improve medication penetration.
- Prompt diagnosis and treatment are crucial as fungal keratitis can progress rapidly and lead to permanent vision loss.
Recent Guidelines
A recent study published in 2024 1 discusses the preferred practice pattern for bacterial keratitis but also touches on the importance of distinguishing between bacterial and fungal keratitis, as the treatment approaches differ significantly. It highlights the risks associated with the use of corticosteroids in the presence of fungal infections, emphasizing the need for careful diagnosis and treatment planning.
Treatment Approach
The use of antifungal medications as the first line of treatment for fungal keratitis is supported by the most recent and highest quality evidence. Given the potential for severe outcomes, including permanent vision loss, it is critical to prioritize antifungal therapy over antimicrobial therapy in cases of fungal keratitis. The choice of antifungal agent and the duration of treatment should be guided by the severity of the infection, the specific type of fungus involved, and the patient's response to therapy, as informed by the latest clinical guidelines and evidence 1.
From the FDA Drug Label
INDICATIONS AND USAGE: NATACYN ® (natamycin ophthalmic suspension) 5% is indicated for the treatment of fungal blepharitis, conjunctivitis, and keratitis caused by susceptible organisms including Fusarium solanikeratitis. For fungal keratitis, the preferred treatment is an antifungal agent, such as natamycin.
- The drug label does not support the use of antimicrobial agents for the treatment of fungal keratitis.
- Antifungal therapy should be determined by the clinical diagnosis, laboratory diagnosis by smear and culture of corneal scrapings and drug response 2.
From the Research
Fungal Keratitis Treatment
- Fungal keratitis is a serious infection of the cornea that requires prompt treatment with antifungal medications 3, 4, 5, 6, 7.
- The most commonly used antifungal medications for fungal keratitis are natamycin, voriconazole, and amphotericin B 3, 5, 6, 7.
Comparison of Antifungal Medications
- Studies have compared the effectiveness of natamycin and voriconazole in treating fungal keratitis, with some showing that natamycin is more effective in achieving clinical cure and preventing corneal perforation or therapeutic keratoplasty 5, 6, 7.
- Natamycin has been shown to result in better visual acuity after infection compared to voriconazole 6, 7.
- Voriconazole has been associated with a higher risk of therapeutic keratoplasty compared to natamycin 6.
Treatment Outcomes
- The outcome of treatment for fungal keratitis can vary depending on the severity of the infection, the type of fungus involved, and the effectiveness of the antifungal medication used 4, 5, 6.
- Penetrating keratoplasty (PKP) may be necessary in severe cases of fungal keratitis that do not respond to antifungal medication 4.
- The use of antifungal medications in combination with other treatments, such as debridement of the ulcer, may improve treatment outcomes 3, 4.
Future Research Directions
- Further research is needed to evaluate the effectiveness of different antifungal medications in treating fungal keratitis, particularly in relation to the type of fungus involved 5, 6.
- Studies should aim to provide high-quality evidence to inform treatment decisions and improve outcomes for patients with fungal keratitis 5, 6, 7.